Silicon carbide (SiC) is expected to be used as a semiconductor material for a power device because of its high electron mobility and high breakdown voltage. Typically, a sublimation method (i.e., modified Lely Method) and a chemical vapor deposition (CVD) method are known as a method for manufacturing a SiC single crystal, which is used for a substrate of the power device. In the modified Lely Method, a SiC material is inserted in a graphite crucible, and a seed crystal (i.e., substrate crystal) is placed on an inner wall of the crucible in such a manner that the seed crystal and the SiC material can face each other. Then, the SiC material is heated to a temperature of from 2200° C. to 2400° C. to generate a sublimation gas, and the submission gas is recrystallized on the seed crystal that is lower in temperature than the SiC material by tens to hundreds of degrees Celsius. Thus, a SiC single crystal is grown on the seed crystal.
According to the modified Lely Method, the SiC material decreases with growth of the SiC single crystal. Therefore, the growth of the SiC single crystal is limited to a predetermined amount that depends on the amount of the SiC material. The growth of the SiC single crystal may be increased by adding additional SiC material. However, in this case, a Si/C ratio exceeds one during sublimation of SiC. Therefore, the addition of the SiC material causes the sublimation gas concentration and the sublimation rate in the crucible to vary. As a result, the quality of the SiC single crystal is reduced.
U.S. Pat. No. 5,704,985 corresponding to JP-11-508531A discloses a method for epitaxially growing SiC by the CVD method. In the CVD method, a seed crystal is placed in a cylindrical reactive pipe (i.e., susceptor), and a material gas containing Si and C is supplied to grow a SiC single crystal on the seed crystal. The CVD method can successively supply the reaction gas so that the SiC single crystal can be grown for a long time.
However, according to the CVD method, a SiC crystal is deposited and grown on not only the seed crystal but also on unwanted portions such as an inner surface of the reactive pipe and a material gas outlet. Due to the growth of the SiC crystal on the unwanted portions, the supply of the material gas cannot be continued. As a result, the growth of the SiC single crystal on the seed crystal is stopped.
In US 2008/0022923, a hole is formed in the crucible, and a deposition prevention gas is introduced through the hole to prevent clogging of the material gas outlet. However, the deposition prevention gas may prevent the deposition only near the hole.